two times the brake rate dropped belowe 150 bps and the fuses popped i'm
pretty sure that they where firewheel faults.
I use a 60 cm fr10 disc with 12 slabs of tungsten 5 by 50 by 75mm at 2000
rpm . stationary gaps are 10mm thick tungsten slabs.
dwell time must be low with the 5mm contact passing by at roughly 100m/s
\
\> Wow, that indeed sounds like a well designed charging reactor for that
> system! Amazing.
>
> Do you have some specs of your rotary also? With 700bps I guess you are
> using one big disc with at least 10 electrodes to keep the speed and
> therefore mechanic stress on the disc relatively low. Or are you using a
> full metal disc + insulating shaft? That would make higher speeds possible
> with not so much electrodes. What is the diameter of your electrodes?
>
> By the way, what is your experience with very low break rates? Did you try
> out, at which speed the spark gap ignites a "firewheel"? Your reactor is
> only 500mH so I think low break rates are particulary critical, because
> the
> current through the reactor rises at a very fast rate, when the power
> supply
> is short circuited accros the closed gap through the reactor and it opens
> to
> slow at low break rates? What are your observations?
> My system is designed for 400bps with a 12,4H reactor, but until now I
> didn't dare to gow below 200bps altough there where no signs of any
> problems, I guess I could go even down to 100bps, will have to try this :)
>
> Regards,
> Stefan
>
>
>
> ----- Original Message -----
> From: <vam@xxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Friday, January 02, 2015 6:45 PM
> Subject: Re: [TCML] Need some advice on 150kva sgtc
>
>
>> Stefan thanks for your observations.
>> The reactor is wound around a 50 kva 3 fase core with the middle leg
>> removed. and cut in halve to introduce two air gaps. it has 10 sections
>> on
>> both legs with 2.5^2 mmm and 200 turns, so about 2000 turns. i lost the
>> calculations, but it was the most challeging part to calculate. it will
>> not saturate.
>> I'm well aware of the 10 amp charging current.
>> i choose a large primairy capacitance to compensate for the relatively
>> low
>> 32 kv end voltage. i think that's pretty high anyway.
>> The coil should work nicely at 200 bps and anything above should be a
>> bonus.
>> I added a new post with a hopefully working link to a picture of the
>> coil.
>>
>>
>>> Maybe you have some saturating issues with your charging reactor, is it
>>> designed properly to handle the massive charging current without
>>> saturation?
>>> Taking your numbers, that gives a maximum power of 143kW @ 700bps and
>>> therefore a charging reactor inductance of only 518mH. The RMS charging
>>> current through the choke is 9,9Amps. Designing such an inductor is a
>>> challenging task, also needs some thick wire to handle 10Amps of
>>> charging
>>> current.
>>>
>>> Another "problem" I see in your supply transformer, with only 10kV it
>>> leads
>>> to big currents, primary capacitance and much to high break rates in
>>> the
>>> whole system, for processing the desired power of 150kW. For such a big
>>> system it would be better to use an AC supply voltage in the range of
>>> at
>>> least 15 or better 20kV. Your 80kV caps wouln't have any problems with
>>> that.
>>> Regarding maximum break rate, different coilers also reported, that
>>> there
>>> is
>>> no big improvement in performance above the 400bps level.
>>> Regarding spark gap, in my opinion it is better, to not exceed
>>> 400-450bps,
>>> but therefore using other tricks to achive a good dwell time and gap
>>> opening
>>> speed. By the way, when using more than 4 series gaps in the rotary, it
>>> also
>>> becomes a problem to "ingnite" the charging system, when using only
>>> 10kV
>>> AC
>>> (~14kV DC).
>>>
>>> Regards,
>>> Stefan
>>>
>>> ----- Original Message -----
>>> From: <vam@xxxxxxxxx>
>>> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>>> Sent: Friday, January 02, 2015 9:43 AM
>>> Subject: Re: [TCML] Need some advice on 150kva sgtc
>>>
>>>
>>>> Hi Carlos.
>>>>
>>>> The streamer length increases significantly from 100-200 bps. 200-600
>>>> there is only a slight increase, probably ads only 50-70 cm to the
>>>> streamer length.
>>>> The 2.2kw sparkgap motor can't get the disc to spin over 700 bps.
>>>> The 125 amp fuses can only take 700 bps for a short while before they
>>>> pop.
>>>> The coil jumps to two steady streamers at this power level.
>>>> We had primairy to secondairy flash over at 700 bps, so the coil is in
>>>> repair now. This led me to believe that the coupling is already too
>>>> high.
>>>> It's .2 acoording to javatc. Playing around with the coupling is not
>>>> so
>>>> easy with a 250 kilo secondairy and topload. We think about installing
>>>> a
>>>> carjack or something like that.
>>>> The sparkgap quenches at second notch with airstreamers and firstnotch
>>>> in
>>>> ground strikes.
>>>> Highering the coil will probably help some because it easily finds
>>>> it's
>>>> way to the floor. We might ad a smaller topload so we can higher the
>>>> main
>>>> topload.
>>>>
>>>>> It would be intersting to see how arc length would improve if you
>>>>> lift
>>>>> the coil up a bit off the ground, and increase the BPS rate.
>>>>> Coupling is also pretty important on big coils...
>>>>> Have you experimented with increasing the coupling at all?
>>>>>
>>>>> Carlos
>>>>>
>>>>> On 2015-01-02 08:13, vam@xxxxxxxxx wrote:
>>>>>> You got my message spot on Carlos.
>>>>>> The coil produces constant streamers about 20- 23 feet, or 6 - 7
>>>>>> meters.
>>>>>> It's very impressive. But i did make a coil with 1 m winding length
>>>>>> before, producing 3 meter sparks at 20 kw.
>>>>>> so i expected around 10 meters with this set up. but 7 seems the
>>>>>> max.
>>>>>>
>>>>>>> Big machines like this are typically less efficient than there
>>>>>>> smaller
>>>>>>> brothers and sisters.
>>>>>>> I have not taken the time to run the numbers on the info you
>>>>>>> provided,
>>>>>>> but if the system is well balanced and in tune and pulling 40kva, I
>>>>>>> would expect to see 20-25 foot long arcs at minimum.
>>>>>>> The height of the coil will also be a limiting factor to some
>>>>>>> degree...
>>>>>>>
>>>>>>> I assume from your question that you are not happy with the
>>>>>>> performance
>>>>>>> or it did not meet your expectations?
>>>>>>>
>>>>>>> Kind regards,
>>>>>>>
>>>>>>> carlos
>>>>>>>
>>>>>>> On 2015-01-02 06:03, vam@xxxxxxxxx wrote:
>>>>>>>> Me and some friends built this coil. It's total height is 5
>>>>>>>> meters.
>>>>>>>> the
>>>>>>>> donut is 2,60 by 60 cm. the coil is 65 cm dia with 1200 turns of
>>>>>>>> 2.5^2mm
>>>>>>>> installation wire. about 3.6 meter winding length. Cap, DR
>>>>>>>> resonance
>>>>>>>> 100nF, 80kv 4 in parallel.
>>>>>>>> We feed it with a 180kva 10kv yz5 transformer. Rectify the lot to
>>>>>>>> 16kv.
>>>>>>>> ballast ensures 32kv on the cap. at 200 bps we draw 50-60 amps per
>>>>>>>> fase.
>>>>>>>> so roughly 40 kw. Max bps is 700.
>>>>>>>> Now the question. What kind of spark length should be possible
>>>>>>>> from
>>>>>>>> this
>>>>>>>> coil?
>>>>>>>>
>>>>>>>> Picture of the coil.
>>>>>>>> https://www.facebook.com/photo.php?fbid=671287332969054&set=a.110176789080114.14601.100002633816524&type=1
>>>>>>>>
>>>>>>>> _______________________________________________
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>>>>>>> Tesla mailing list
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>>>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>> _______________________________________________
>>>>> Tesla mailing list
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>>>>>
>>>>
>>>>
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>>>
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>>
>>
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